A problem associated with well vertical pumps and their rotating parts is the overheating of bearings in which the parts rotate. Bearing overheating may be the result of (1) the breaking down of the chemical integrity of a lubricant with a consequent loss of lubricating qualities or (2) the interruption of the flow of lubricant through narrow passages through the bearings and packings.
In the latter case, for instance in a typical well pump system, the needle valve that regulates the flow of oil in the oil-lubricated, vertical turbine pump becomes clogged easily. The oil is gravity fed from an oil container drum and regulated through a sight gauge by an adjustable needle valve to provide a flow of approximately 6 to 8 drops per minute. It is delivered to the top bearing of the well through a 1/4" copper tube and then through grooves cut in the top bearing and the rest of the well bearings, which are spaced at five foot intervals, all the way down to the bottom of the well where the pump bowls are located. The needle valve regulator is sensitive to moisture, dust and various foreign particles that are present in farm environments, all of which cause clogging in the needle valve. The consequent loss of oil flow causes increased friction which, in turn, permits the pump shaft and bearings to overheat. Sixty-five minutes after the lubricant flow interruption, temperatures in a lineshaft may exceed 400 F. (the flash point of common motor oils), causing residual oil in the shaft to vaporize. If the pump continues operation thereafter without lubrication the bearing temperature will exceed 1100 F. in less than one hour, causing a typical bronze bearing to experience massive wear very quickly and to flake off into the oil chamber and onto the bearing below, resulting in pump shaft failure.
Pump shaft failure involves expensive repairs and loss of service while the well is down. For example, in agriculture, crucial periods in crop growth require a constant supply of irrigation water; consequently, any significant loss of water supply at such times results in partial or complete crop failure
Prior art patents offer some suggestions for dealing with the problem of bearing failure resulting from excessive temperature. Heckert (U.S. Pat. No. 2,089,369) described an overheated bearing and journal detection and identification system associated with wheel axles of railway cars. Heckert's heat detection system relied on the melting point of a fusible closure disk intimately associated with a journal box and a bearing.
Others have resorted to the use of various temperature sensing means imbedded in the bearing itself or, alternatively, in the bearing housing support to detect and monitor bearing temperatures (Waseleski et al, 3,824,579; Bergman et al 4,074,574; Gustafson 3,052,123; Reumund 2,964,875). However, because bearings associated with well pumps are located within oil tube lineshaft encasements surrounded by flowing water, temperature sensors embedded in such bearings may be inaccurate and their temperature readings unreliable. Even the flow of water below the bearing affects the temperature perceived by a sensor embedded in the bearing. Sometimes a packing heats up instead of a bearing, but a sensor imbedded in the bearing is not sensitive to the packing temperature, and it is not practical to embed a sensor in the packing.